The utilization ofthe low-temperature waste heat of flue gases from thermal conversion processes for power generation has failed hitherto because of the low economic efficiency of the units operating in tandem.
The relatively low exhaust gas temperatures of these waste heat sources, which are subject to great variations due to the process, made possible only low steam parameters before. The electric efficiency of the power generation in a generator in cooperation with a steam turbine was characterized by measures to reach a suitable steam temperature and steam pressure.
A combination power plant with a gas turbine power plant and with a steam power plant has been known from DE 195 23 062 A1.
In this combination power plant with a gas turbine power plant and with a steam power plant, a steam turbine plant is operated with the steam of a steam generator equipped with firing equipment and/or with the steam of a waste heat boiler, through which the exhaust gas of the gas turbine flows. A heat exchanger is provided for the controllable preheating of the compressed combustion air of the gas turbine plant. To operate the combination power plant especially economically even in partial load operation, the heat exchanger for the combustion air of the gas turbine plant is arranged in the flue gas duct of the steam generator and is designed as a recuperator, wherein the flue gas is led around the pipes of the recuperator and the combustion air is led though the pipes ofthe recuperator. The recuperator is connected via a three-way valve and a bypass to the combustion air line leading from the compressor to the gas burner of the gas turbine plant.
A thermal power plant with a gas turbine and with a steam generator for a multi-pressure steam turbine has been known from the yet unpublished DE 197 34 862.9, wherein the exhaust gas of the gas turbine is fed to a waste heat boiler, which is equipped with auxiliary firing equipment to raise the high pressure (HP) steam output and which contains heat exchangers intended for generating steam. To make it possible to generate steam economically for a multi-pressure steam turbine, especially also at varying loads, three series-connected HP superheater stages with two spray coolers are provided for generating high-pressure steam, and two intermediate-pressure (IP) superheater stages with a spray cooler are provided for generating an intermediate-pressure (IP) steam. The end stages of the HP superheater and IP superheater are arranged in the same section ofthe waste heat boiler, and their tubes are located alternatingly next to one another in a comb-like pattern. The first IP superheater stage is located between or behind the first two HP superheater stages. A first firing equipment utilizing the exhaust gas of the gas turbine is arranged in the area of the end stages of the superheaters, and a second firing equipment is arranged in front ofthe HP evaporator, wherein the first firing equipment is controlled as a function of the temperature of the steam at the outlet of the first IP superheater stage, and the second firing equipment is controlled by the HP load in a pressure-dependent manner.